I would suggest a "termal vent" technology that triggers with 50 crafted iron plates and unlocks the thermal-vent recipe instead of having it automatically unlocked when starting on vulcanus.
This way power is unlocked in a similar way like the steam-power on nauvis.

Thanks for the suggestion Pithlit, I had the same thought and so I've made it so the generator unlocks when mining one of the Vulcanus chimney vents, which should make it more contextual for Vulcanus, as well as not showing up on other planet starts where it's useless.